Hmmm my dd Ped even when she was a few months old said I could give her an ounce of formula now and then, he said, babies get thirsty too. My dd loved water so I really had to watch how much she took but never had any bad reactions from her having an ounce. Also, I never gave water from the bottle, I always gave it out of a sippy cup, even when she was just a few months old.